Tropical Storm Don (Updated: 1:00pm CDT, 7/28/2011)

Watches/Warnings:
A TROPICAL STORM WARNING IS IN EFFECT FOR…
* TEXAS COAST FROM PORT MANSFIELD TO SAN LUIS PASS

A TROPICAL STORM WATCH IS IN EFFECT FOR…
* TEXAS COAST SOUTH OF PORT MANSFIELD TO THE MOUTH OF THE RIO GRANDE

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 36 HOURS.

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA…GENERALLY WITHIN 48 HOURS.

Here is the latest on TS Don, as of 12:40pm CDT:

LOCATION…24.6N 90.7W
ABOUT 475 MI…765 KM ESE OF CORPUS CHRISTI TEXAS
ABOUT 430 MI…690 KM E OF BROWNSVILLE TEXAS
MAXIMUM SUSTAINED WINDS…45 MPH…75 KM/H
PRESENT MOVEMENT…NW OR 305 DEGREES AT 15 MPH…24 KM/H
MINIMUM CENTRAL PRESSURE…1005 MB…29.68 INCHES

Figure 1. NHC's forecast storm path for TS Don.

If you may have noticed, the pressure of TS Don has gone up a few millibars from previous hours.  This mean it has weakened just a bit.  Winds did go up a little, but the overall structure of the storm took a hit.  The storm’s northeast section is experiencing some moderate wind shear, which is why Don is having a hard time developing further.  There is also subsiding (sinking) air ahead of the storm that might also be cause some trouble for development of the storm. None of the models have the storm strengthening over 55 mph max wind speeds at landfall anymore.  There is still some questions as far as the path of the storm. Forecasting models are beginning to concise in an area between Baffin Bay and Matagorda Bay.  Both of these areas are north of the Rio Grande Valley.  This does not mean that we are out of the picture.  Models are still waffling around an exact area.  Depending where and how strong the storm is will determine how much rain the Valley gets.  Surprisingly,as it is looking right now, the more disorganized and the further south the storm were to hit (closer to Baffin Bay) would be the greatest chance of rain for the RGV.

Any direct hit north of Corpus Christi would decrease showers and thunderstorms chances to a minimum, especially if the storm stengthens.  And although the RGV doesn’t need a half foot of rain, we do need some rain because we are still under a drought. Below are two images.  One shows the wind shear at mid-levels and the other image is a water vapor satellite imagery taken around 1:00pm CDT.

Figure 2. Mid-level wind shear around TS Don may cause it to stop strengthening. Darker colors (black/blue) indicate lower wind shear values.

Figure 3. Water vapor satellite imagery showing where the water vapor is vs. dry air. TS Don is moving WNW into the drier air. Darker colors indicate dry air.

 

About Brian

University of Oklahoma graduate with a degree in Meteorology. Follow me on Twitter: @WeatherInformer
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